Squeezing from Raman Scattering in Optical Parametric Oscillators

Abstract

The squeezing properties of the Raman scattering process which takes place when the lower output frequency from a non-degenerate optical parametric interaction approaches a resonance of the nonlinear medium placed inside an optical resonant cavity are presented. The linear stability analysis is performed and the spectrum for the output fields is given in terms of the quadrature phase components in the Wigner representation. Perfect squeezing for the amplitude difference between the output Stokes and anti-Stokes modes at the Hopf bifurcation point is obtained.     

Amplitude-squared and amplitude-cubed squeezing in stimulated Raman and in spontaneous Raman scattering

Coherent light coupled to a third-order nonlinear medium is responsible for spontaneous and for stimulated Raman processes. The analytical solutions up to second order in coupling constants of various field modes for spontaneous Raman and for stimulated Raman processes are utilized to obtain the amplitude-squared and amplitude-cubed squeezing of the input coherent light. The amplitude-squared and amplitude-cubed squeezing are completely ruled out for all modes for spontaneous Raman processes. For stimulated Raman processes, we observe that the squeezing for amplitude-squared and amplitude-cubed are possible for pump and for vibrational phonon modes. It is found that the percentage of higher ordered amplitude squeezing decreases with the increase of the orders. The squeezing in Stokes and in anti-Stokes modes are ruled out even for stimulated Raman processes.     

Stimulated Raman Scattering of Squeezed Light with Pump Depletion

Abstract

Using the approximation of small fluctuations around a stationary point, photon statistics and squeezing of vacuum fluctuations are derived in stimulated Raman scattering including the coupling of photon-photon and photon-phonon modes. The depletion of pump light is described and it is shown that a regime of inversion of the process is related to an increase in quantum fluctuations, which are finally reduced again, more in the anti-Stokes mode than in the Stokes mode. If the anti-Stokes coupling is stronger than the Stokes coupling, then an oscillating behaviour of the statistical characteristics occurs and substantial squeezing can be found in photon-phonon modes.     

Comments on ‘Higher order squeezing of the electromagnetic field in spontaneous and in stimulated Raman processes’

Of late, Giri and Gupta [J. Mod. Opt. 52 1769 (2005)] discussed the possibility of getting higher order (fourth and fifth orders) squeezing of the fundamental mode in spontaneous Raman and in stimulated Raman processes. These investigations are based on the earlier works of Kumar and Gupta [Quantum Semiclass. Opt. 7 835 (1995)]. We reinvestigate the model and we found that the entire calculations and hence the conclusion of Giri and Gupta and Kumar and Gupta are not only baseless but also misleading. There will be no squeezing of the fundamental mode in spontaneous and in Raman processes.     

Control of enhanced Raman scattering using a DNA-based assembly process of dye-coded nanoparticles

Enhanced Raman scattering from metal surfaces has been investigated for over 30 years. Silver surfaces are known to produce a large effect, and this can be maximized by producing a roughened surface, which can be achieved by the aggregation of silver nanoparticles. However, an approach to control this aggregation, in particular through the interaction of biological molecules such as DNA, has not been reported. Here we show the selective turning on of the surface enhanced resonance Raman scattering effect on dye-coded, DNA-functionalized, silver nanoparticles through a target-dependent, sequence-specific DNA hybridization assembly that exploits the electromagnetic enhancement mechanism for the scattering. Dye-coded nanoparticles that do not undergo hybridization experience no enhancement and hence do not give surface enhanced resonance Raman scattering. This is due to the massive difference in enhancement from nanoparticle assemblies compared with individual nanoparticles. The electromagnetic enhancement is the dominant effect and, coupled with an understanding of the surface chemistry, allows surface enhanced resonance Raman scattering nanosensors to be designed based on a natural biological recognition process.     

斜坡海涂上修建海堤的爆炸挤淤施工技术

采用爆炸挤淤置换法在较陡的斜坡海涂上修筑海堤,因堤身内外侧涂面高差大,施工过程中抛填堤身容易滑塌。最初在浙江舟山某海堤工程中遇到了这个难题。通过对堤身稳定性的计算分析,将堤身抛填方法调整为"内侧突前、外侧迟后",炸药布置侧重于内侧。既保证了施工期抛填堤身的稳定,又使得爆炸处理后形成的堤身断面满足设计要求。此后该方法又在多条类似海堤的施工中得到成功的应用,由此总结出了在斜坡海涂上修建海堤的爆炸挤淤技术,并申报了发明专利(201510908384.1)。     

斜坡海涂上修建海堤的爆炸挤淤施工技术

采用爆炸挤淤置换法在较陡的斜坡海涂上修筑海堤,因堤身内外侧涂面高差大,施工过程中抛填堤身容易滑塌。最初在浙江舟山某海堤工程中遇到了这个难题。通过对堤身稳定性的计算分析,将堤身抛填方法调整为"内侧突前、外侧迟后",炸药布置侧重于内侧。既保证了施工期抛填堤身的稳定,又使得爆炸处理后形成的堤身断面满足设计要求。此后该方法又在多条类似海堤的施工中得到成功的应用,由此总结出了在斜坡海涂上修建海堤的爆炸挤淤技术,并申报了发明专利(201510908384.1)。     

The role of squeezing in quantum key distribution based on homodyne detection and post-selection

Abstract

The role of squeezing in quantum key distribution with continuous variables based on homodyne detection and post-selection is investigated for several specific eavesdropping attacks. It is shown that amplitude squeezing creates strong correlations between the signals of the legitimate receiver and a potential eavesdropper. Post-selection of the received pulses can therefore be used to reduce the eavesdropper's knowledge of the raw key, which increases the secret key rate by orders of magnitude over large distances even for modest amounts of squeezing.     

挤淤爆破规律及其振动效应研究

为了研究挤淤爆破规律以及爆破地震波的传播特性,结合连云港连云新城示范区填海造地及基础设施建设项目的挤淤爆破工程实例,对挤淤爆破的全过程进行高速摄影录像和爆破地震波监测与分析。高速摄影再现了挤淤爆破过程中"水—淤泥—围堰"系统相互作用的运动过程,有效解释了挤淤爆破过程中预埋石料与淤泥置换的作用机理。利用实测的爆破地震波数据修正与地形地质条件有关的系数K和衰减系数α,获得了适于挤淤爆破过程中计算质点振动速度随距离衰减的Sadovsk计算公式,为有效预测类似工程中爆破地震波的传播规律特征提供了一种方法参考。挤淤爆破过程中测得的爆破地震波主振频率范围在8~50 Hz之内,说明淤泥介质对爆破地震波不同频率成分的传播具有选择性:高频地震波通过淤泥时产生大幅度的衰减,低频地震波通过淤泥后对建(构)筑物造成破坏。     

精密硅片台步进扫描运动的5阶S曲线规划

为降低硅片台在曝光扫描过程中的加减速时间以及提高扫描速度的平稳性,设计了5阶对称S曲线。设定加速度三阶导数为恒定值,通过向上积分的方法确定了5阶S曲线的位置和速度表达式。以时间最优和冲击最小设计优化指标,对步进过程的5阶轨迹进行优化,设计了改进5阶S曲线。仿真结果表明,5阶S曲线可以使硅片台在短时间内加速到扫描速度,并且可以快速稳定。改进5阶S曲线大幅度缩短步进时间,硅片台步进曲线平滑无突变。     

Quantum Statistics of Stimulated Raman and Hyper-Raman Scattering of Squeezed Light with Pump Depletion

Abstract

Using the approximation of small fluctuations around a stationary solution, photon statistics and quadrature variances are derived in stimulated Raman and hyper-Raman scattering including the coupling of pumping, Stokes, anti-Stokes and phonon modes. The depletion of pump light is included. Compared to Raman scattering, additional regimes to generate anti-bunched, sub-Poisson and squeezed light were found caused by self-interaction of the pump mode. It was possible to include effects of nonlinear dynamics, initial squeezing of radiation and phonon system, external noise and losses.     

Coexistence of interfacial stress and charge transfer in graphene oxide-based magnetic nanocomposites

In this paper, the existence of both compressive stress and charge transfer process in hydrothermally synthesized cobalt ferrite–graphene oxide (CoFe₂O₄/GO) nanocomposites has been established. Transmission electron microscopy results reveal the decoration of CoFe₂O₄ nanoparticles on GO sheets. Magnetic response of nanocomposites was confirmed from superconducting quantum interference device magnetometer measurement. Optical properties of these nanocomposites were investigated by Raman spectroscopy. The interfacial compressive stress involved in this system has been evaluated from observed blue shift of characteristic G peak of graphene oxide. Increase in the full-width half-maximum value as well as upshift in D and G peaks is clear indications of involvement of charge transfer process between GO sheets and dispersed magnetic nanoparticles. The effect of charge transfer process is quantified in terms of shifting of Fermi energy level of these nanocomposites. This is evaluated from variation in contact surface potential difference using scanning Kelvin probe microscopy. XRD spectra of CoFe₂O₄/GO confirm the polycrystalline nature of CoFe₂O₄ nanoparticles. Lattice strain estimated from XRD peaks is correlated with the observed Raman shift.     

Resonant Raman and micro-Raman scattering from Si matrix with unburied beta-FeSi2 nanolayers

Samples, representing Si matrix with nanolayers of the semiconducting beta-FeSi2 silicide are studied by Raman scattering. The unpolarized Raman spectra of the samples are measured in two different configurations. It is found that the characteristic beta-FeSi2 Raman modes are seen in the spectra, taken at incident angle of about 45 degrees , while only comparatively intensive broad feature is detected in a back-scattering geometry. The difference in the spectra is interpreted with the appearance of surface polariton modes of the optical phonons in the nanosized layers in near back-scattering geometry. The resonant Raman scattering is investigated at incident light angle of about 45 degrees and the energies of the interband transitions in the investigated energy range are determined. It is known that the resonant Raman scattering appears to be even more precise method for the determination of the interband transitions energies than the modulation spectroscopy. Thus we claim that the energies determined here are firstly determined with such a precision.     

Coherent States of a Harmonic Oscillator in a Finite-dimensional Hilbert Space and Their Squeezing Properties

Abstract

New coherent states of a harmonic oscillator in a finite-dimensional Fock space are introduced. Some properties of these coherent states are discussed. The second-order squeezing of these coherent states with respect to the quadrature operators is studied in detail. In particular, for a two-state system the arbitrary higher-order squeezing of these states is investigated. It is shown that these coherent states exhibit much richer squeezing properties than the coherent states of a usual harmonic oscillator in an infinite-dimensional Fock space. It is found that these coherent states have not only second-order squeezing but also higher-order squeezing with respect to the quadrature operators of the field under consideration.     

Squeezing of light field in a dissipative Jaynes–Cummings model

Based on the time-convolutionless master-equation approach, we investigate squeezing of light field in a dissipative Jaynes–Cummings model. The results show that squeezing light can be generated when the atom transits to a ground state from an excited state, and then a collapse-revival phenomenon will occur in the squeezing of light field due to atom-cavity coupling. Enhancing the atom-cavity coupling can increase the frequency of the collapse-revival of squeezing. The stronger the non-Markovian effect is, the more obvious the collapse-revival phenomenon is. The oscillatory frequency of the squeezing is dependent on the resonant frequency of the atom-cavity.     

A Preliminary Raman Investigation of the Lead Titanate Thin Films via Sol-Gel Process

Raman spectra of the PbTiO3 films via sol-gel process were investigated by using a Jobin Yvon U1000 system. Compared with the Raman spectra of the PbTiO3 single crystals, Raman peaks of PbTiOs films shift downward, which is attributed to the stress effect in the PbTiO3 films exerted by the substrate and the size effect on the Raman frequencies     

Squeezed states in spontaneous Raman and in stimulated Raman processes

The Hamiltonian and the equations of motion for various modes involving spontaneous and stimulated Raman processes are derived. The coupled differential equations involving these modes are solved analytically by using an intuitive approach (IA). The solution of the present paper does not require any short time approximation. As a matter of fact, the present solution for field operators and hence the squeezing for various modes are valid for all interaction time t. In this way, the present paper is more general compared to the earlier investigations where short-time approximations were found a must. By exploiting the solutions for the field operators, we obtain the squeezing effects of input coherent light for pure and for mixed field modes. The IA employs the perturbation theory and hence we came across the secular terms in the solution. Of course, for small coupling constants these secular terms could be summed for all orders. To establish our claim, we remove the secular terms at least for one occasion.     

Effective Dipole Squeezing in the Non-degenerate Two-photon Jaynes-Cummings Model with Superposition State Preparation

Abstract

Effective dipole squeezing in the non-degenerate two-photon Jaynes-Cummings model for atom and fields initially prepared in superposition of states is investigated. It is shown that the squeezing can be exhibited in certain periods of time but it cannot be achieved for atomic spontaneous radiation processes.     

Characterization and micromechanical testing of the interphase of aramid-reinforced epoxy composites

The properties of the interphase between Twaron^® aramid fibres and polymer matrix systems can be optimized by a surface treatment process of the fibres. The relation between this surface treatment, the resulting chemical and physical surface structure, as measured with XPS, IGC and SFM, and the adhesion strength in fibre–epoxy systems, as measured with Raman spectroscopy and single-filament pull-out experiments, has been established and related to the macromechanical data of real composites. The concept of local bond strength was used and the fibre–epoxy failure mechanism investigated.